Along with the development of economy and society, petroleum resources are increasingly scarce and show inferior and heavy trends, thus, heavy and inferior crude oils are required to be processed so as to make the heavy and inferior crude oils into light oils. In the field of petrochemical industry, a suspended-bed hydrogenation process is an optimal way for light oil conversion of heavy/inferior oil such as heavy oil, residual oil and high-temperature coal tar, and the technology can be used for treating heavy/inferior oil feedstocks with higher metal and sulfur content and has the characteristics of high feedstock adaptability, simple process, high conversion ratio and demetalization ratio, high light oil yield, and so on, thereby being extensively used.
Among numerous conditions affecting the suspended-bed hydrogenation process, the hydrogenation catalyst is undoubtedly the most important factor, and the quality of the hydrogenation catalyst can directly affect the demetalization ratio and light oil yield of a light oil conversion process of the heavy and inferior crude oils. The existing suspended-bed hydrogenation catalysts can be generally divided into three major categories, i.e., solid-particle catalysts, loaded type catalysts and dispersed type catalysts, wherein the loaded type catalysts are extensively applied to the suspended-bed hydrogenation process due to the advantages of simplicity in preparation, easiness in morphology control, good coking inhibiting properties, recyclability, etc. The loaded type catalysts are composed of supports and active components, and the catalytic performance of the loaded type catalysts lies on the inherent catalytic characteristics of the active components, the properties of the supports and the load characteristic between the active components and the supports, so that improvement on the catalytic activity of the loaded type catalysts is facilitated through reasonably proportioning the supports and the active components.
For example, a preparation method for a residual oil hydrotreating catalyst is disclosed by a Chinese Patent Document CN 104588079 A. The method comprises the steps: (1) subjecting an aluminium alkoxide compound and water to a reaction in the presence of an organic solvent, adding a Y-type molecular sieve during the reaction, controlling the pH value of the system to 1 to 6, and carrying out filtering after the reaction is completed to obtain a filter cake; (2) adding the filter cake obtained in the step (1) into aluminium hydroxide based dry glue powder, uniform mixing the filter cake and the aluminium hydroxide based dry glue powder, and carrying out molding, drying and calcining, thereby obtaining a Y-type molecular sieve and aluminum oxide composite catalyst support; and (3) impregnating the composite catalyst support into an active-metal solution, and carrying out drying and calcining, thereby obtaining the catalyst. In the above-mentioned technology, through the mutual coordinating action between the Y-type molecular sieve and aluminium hydroxide, the finally-prepared catalyst facilitates approaching and cracking of macromolecular hydrocarbons, meanwhile, the production of carbon deposit can be reduced, and the carbon residue removing activity and stability of the catalyst can be improved. However, the catalyst prepared by the above-mentioned technology has a relatively small and relatively single pore size, the ratio of pores with a pore size of 6 nm to 15 nm accounts for 70% or more, thus, the catalyst has poor adsorption capacity to asphaltenes and colloids with high molecular weight, the asphaltenes and colloids are difficult in cracking, and thus, the yield of light oil products is relatively low; in addition, because the asphaltenes and colloids deposited on the catalyst can block up pore passages and cover active centers, the activity of the catalyst is lowered.
The composite hydrogenation catalyst subjected to a hydrogenation process is converted into a spent catalyst. Metals such as Fe, Ni, V and Ca in raw oil present in the form of soluble metal-organic compounds, the soluble metal-organic compounds can be decomposed and deposited to the surface and interior of the catalyst to block up micropores of the catalyst during hydrogenation catalysis, meanwhile, carbon can also be deposited to the surface and interior of the catalyst during hydrogenation catalysis and similarly blocks up the micropores of the catalyst and cover active centers of the metals, and finally, catalyst deactivation is caused.
Moreover, original active centers such as nickel and molybdenum in the spent catalyst all present in the form of sulfides, thus, the spent catalysts have inflammability and toxicity, belong to hazardous wastes and are required to be treated.
The conventional catalyst treatment flows are as follows: incinerating the spent catalyst, pulverizing the incinerated material into powder, carrying out oxidizing calcining, carrying out alkaline leaching to recover molybdenum and vanadium, carrying out acidic leaching to recover cobalt and nickel, and discharging waste residues. However, the flows have the following problems: (1) valuable metals such as molybdenum and nickel are incompletely recovered, and the recovery ratio is low; (2) the spent catalyst has an adsorbed oil content of 5% to 15%, oils are burnt and wasted during incinerating, and meanwhile, the environment is polluted; (3) sulfur of metal sulfides is oxidized during incinerating and oxidizing calcining and is converted into sulfur dioxide, and thus, the environment is polluted; and (4) treated waste residues still contain heavy-metal salts, and secondary pollution may be caused in case of long-term stacking and treatment.
A regeneration method for a heavy oil hydrotreating catalyst is disclosed by a Chinese Patent Document CN 102310005 A. Disclosed are the following steps: firstly, carrying out dry distillation on a deactivated heavy oil hydrotreating catalyst, then, carrying out washing by an acidic solution, and then, carrying out calcining decoking treatment, wherein the dry distillation is carried out at a temperature of 300 DEG C. to 550 DEG C., the acidic solution is a hydrochloric acid containing solution, the ratio of the amount of washing acid to the amount of the catalyst is 5 L/Kg to 50 L/Kg, and the acid concentration is 0.1 mol/L to 0.5 mol/L. Through the dry distillation, liquid hydrocarbons are obtained through subjecting part of coking substances to a dry distillation reaction while part of residual oil is recovered from the deactivated catalyst, so that the recovery ratio of valuable products is increased. Through organically integrating the steps such as carrying out dry distillation, carrying out acid pickling and carrying out calcining and proper conditions, the deactivated hydrotreating catalyst is excellently regenerated.
However, known through analysis, the technical scheme disclosed by the above-mentioned patent document has the following defects: (1) supports and active ingredients are not subjected to effective composite utilization in a recovery treatment process of spent hydrogenation catalysts; (2) metal impurities are removed through acid pickling, however, some metal impurities can serve as active metals of a follow-up hydrogenation process, thus, these metal impurities are not effectively utilized; and (3) through dry distillation, the liquid hydrocarbons are obtained through subjecting part of the coking substances to the dry distillation reaction, however, the remaining coking substances are not effectively utilized; and then, carbon deposit is removed through calcining, thus, the carbon deposit is not utilized.